Relative Roughness of pipes - Solving a Three Reservoir Problem

In summary, Xaan's relative roughnesses are smaller than 0.05, which causes problems when solving for Reynold's number and friction factor. He successfully solved the problem by finding the relative roughness unit and using it to solve for the Reynolds number and friction factor.
  • #1
xaan
2
0
Relative Roughness of pipes!

Homework Statement



Here is the Data:

Reservoir Water Entry Pipeline Pipeline Pipeline
Number Level Coeff. Length Diameter Roughness
m [AHD] [m] [m] [mm]
0 20.665 0.814 432.453 1.222 0.089
1 17.787 0.544 111.972 1.361 0.147
2 11.166 0.583 201.258 1.171 0.076


Homework Equations


I need to solve this three reservoir problem, but I'm stuck in finding the Reynold's number and Friction factor from Relative densities. Relative roughness is just (Pipeline Roughness/Pipe Diameter). From Moody Diagram, the highest Relative roughness is 0.05 and I can't see anything higher than that, but the values I get are all higher than 0.05 for relative roughness.


The Attempt at a Solution


Is there a solution to this?
 
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  • #2
Hello Xaan, you're relative roughnesses are smaller than 0.05. Look at the unit of relative roughness and the ones you are given in the table. That should clarify one of your problems. The one for calculating the Reynolds number is something else. Do you know the formula for this? Can you give some more information on how this system looks like? It is a bit unclear for me to understand.
 
  • #3
coomast said:
Hello Xaan, you're relative roughnesses are smaller than 0.05. Look at the unit of relative roughness and the ones you are given in the table. That should clarify one of your problems. The one for calculating the Reynolds number is something else. Do you know the formula for this? Can you give some more information on how this system looks like? It is a bit unclear for me to understand.

Yes I realized that relative roughnesses have to be smaller than 0.05. I had to go back and double check it from where I got the info from, and they told me the units they used was wrong. Instead of mm, they put m for pipe diameter. lol so I solved it and I go all the dischages and their directions:

Q1 + Q2 = Q3

*cheerz!*
 

What is relative roughness of pipes?

Relative roughness of pipes refers to the measure of how rough or smooth the inner surface of a pipe is in comparison to the diameter of the pipe. It is typically represented by the symbol "ε" and is used in fluid mechanics to calculate the frictional losses in a pipe.

How is relative roughness calculated?

Relative roughness is calculated by dividing the average height of surface irregularities on the inner wall of the pipe by the diameter of the pipe. This value is then used in various equations to determine the friction factor and pressure losses in the pipe.

Why is relative roughness important in fluid mechanics?

Relative roughness is important in fluid mechanics because it directly affects the frictional losses in a pipe. A rougher surface will cause more resistance to the flow of fluid, resulting in higher pressure losses and lower flow rates. It is also used in the design and selection of pipes for different applications.

What are the factors that influence relative roughness?

The factors that influence relative roughness include the type of material used to make the pipe, the manufacturing process, and the age of the pipe. Other factors such as the velocity and type of fluid flowing through the pipe can also affect the roughness of the inner surface.

How can relative roughness be reduced?

Relative roughness can be reduced by using smoother materials for pipe construction, such as stainless steel or PVC. Regular maintenance and cleaning of pipes can also help to reduce roughness and maintain a smooth inner surface. Additionally, increasing the pipe diameter can decrease the relative roughness and improve flow efficiency.

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